Out with the Old, In with the New

SOFIA to Replace KAO Flight Observatory -- by Jami Dwyer

The recently-retired Kuiper Airborne Observatory (KAO) gazed deep into the universe for
twenty years. Unfortunately, it also occasionally just looked off into space. New technology
will improve the quality of science done on the flying observatory's replacement, the
Stratospheric Observatory for Infrared Astronomy (SOFIA). Automated balancing of the
in-flight telescope will replace KAO's lengthy manual adjustment system when the Boeing 747
bearing the 2.5-meter telescope (the largest airborne astronomical observatory ever constructed)
takes off in 2001.

This fall, SOFIA is undergoing detailed system design after evaluation of
proposals for prime contracts for the Congress and NASA-approved program. Like its
predecessor, SOFIA will be used for advanced astronomical observations at stratospheric
altitudes in excess of 41,000 feet. The joint project of DARA (the German space agency) and
the National Aeronautics and Space Administration (NASA) will support scientific research in
infrared astronomy by accommodating installation of different focal plane length instruments
provided by investigators from the international science community. SOFIA's automated
balancing technology will allow more instrument changes. They will be able to do 160 science
flights per year for the predicted 20-year life of the facility. This will accommodate 50 PI teams,
and include about 80 instrument changeouts.

KAO, a C-141 based project, employed a highly-skilled technician to balance the telescope by trial and error before flight, and could not
adjust for weight changes due to such things as cryogenics depletion during flight. SOFIA's
efficiency will increase beyond KAO's with an automated control system that will both reduce
the time required to balance the telescope on the ground, and dynamically balance the telescope
in-flight. The DARA-provided telescope system, designed using pattern-recognition techniques,
will be able to recognize the desired area of the night sky by comparing video input from the
tracking camera with star charts. Dynamic balancing will improve pointing accuracy, increasing
the quality of science produced on SOFIA. Further automation still being considered will also
reduce costs in terms of how many people are necessary to keep the telescope on target.

SOFIA will provide an important platform for application of
autonomous systems technologies like the
one that will automatically re-balance the telescope. An example of technology to be tested on
SOFIA is a pressure sensor that can be added as an afterthought to wings and airfoils, as opposed
to current technology that requires construction of custom wings and airfoils, often at a cost
upwards of a million dollars. The technology to be tested on SOFIA consists of light diffraction
gratings whose line spacing will be affected by pressure. The wavelength of light reflected will
indicate how much the line spacing has been altered by pressure changes. Such new technology
will reduce pressure-sensing to several thousand dollars, as well as make installation easier.
Measurements once rejected as too expensive will be taken.

Expanding on KAO's "Live from the Stratosphere" program, the
Education and Outreach Office plans to expand SOFIA mission
participation to include interested citizens like educators, students, the media, amateur
astronomers, and people with scientific interests beyond astronomy who can use SOFIA for their
observations. The program outline describes it as "as close to flying aboard the Space Shuttle as
will ever experience." In addition, the Office requests public input to help design SOFIA, in the
form of a 50 word essay describing what you would do if you could fly aboard SOFIA. Contact
Bob
Hillenbrand for further outreach information.